ABSTRACT
The pn semiconductor junctions exhibit nonlinear current–voltage characteristics, and they are used to rectify and shape electrical signals. Exponential current–voltage characteristics are sometimes used to build logarithmic amplifiers. The thickness of the depletion layer depends on applied reverse voltage, and the voltage-dependent capacitance can be used to tune frequency characteristics of electronic circuits. In the case of common silicon diode, the forward direction current increases exponentially at first, and then it is limited by an ohmic resistance of the structure. A very small current in the reverse direction at first increases slightly with applied voltage and then starts to multiply near the breakdown voltage. The n-type semiconductor material has a positive impurity charge attached to the crystal lattice structure. This fixed positive charge is compensated by free moving electrons with negative charges. The switching time of the pn junction is limited mainly by the storage charge of injected minority carriers into the vicinity of the junction.
